Japanese Patent Application Publication No. 2004-335336 (JP-A-2004-335336) discloses a fuel cell that has a structure for fastening a cell stack as described below. In this fuel cell, a pair of end plates that contact two opposite ends of a cell stack in the stacking direction, and a side member sandwiched between the two end plates are interconnected with a bolt axial force acting substantially in the stacking direction of the cell stack.
In the foregoing fuel cell, the reaction or withstanding force needed to prevent relative displacement between the end plates and the side member due to load from a direction intersecting with the stacking direction of the cell stack is dependent on the axial force of the connecting bolts that connect the end plates and the side member. Therefore, the connecting bolts need to be large in size in order to sufficiently secure the strength of the fuel cell. This gives rise to a problem of a size increase of the fuel cell.